Valve train problems

Kurt Wallis

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I recently purchased a K3500 dually 454ci. The engine was recently rebuilt or they said. It does have all new gaskets and is very clean. After I got it home I did a compression test all cylinders were at 155psi. After driving it around town I noticed that When it's cold it doesn't smoke but When you start it up after you have driven it it puts out a small cloud of blue smoke. I figured the bottom end was rebuilt but he just put the old heads on with out going through them. Then I went on a trip 640mil to hall some furniture. Going there I was empty so it was easy going. All went well till the last gas stop on pulling out as I accelerated at 2000rpm I got a lifter tapping if I left off the gas back down to 2000 it would go away. I could go 75prh at 2600rpm with no noise as long as there was no load on the engine. I pulled the valve covers off all was tight so I came home empty. The hole trip home was the same no load on the engine no noise or below 2000rpm. I thought it might a lifter and cam eating each other as they may not have been matched up When it was put back together. Some have said weak valve spring. My experience with small block engines is broken springs but you have a dead cylinder. This thing ideals fine and runs smooth until you get into it. I am out of ideas
 

Schurkey

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WHAT YEAR VEHICLE/ENGINE??? Flat-tappet cam, or roller cam?

Oil level correct?

Can you narrow down the location of the noise by running the engine in Park or Neutral, and using a mechanic's stethoscope?

Remove valve covers, run engine. All the rocker arms moving about the same amount? Any visible damage to valve springs?

Any chance what you're hearing is detonation, not valvetrain noise? Connect a scan tool, look for knock counts and/or a failed knock sensor.
 

Kurt Wallis

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Sorry that was a lame post
So the details are there is NO check engine light on and no codes. Also there is only One lifter-valve making noise. On the trip from Stl to Pit and back to Stl it used 1.5qt of oil. Oil pressure is 45 to 50 When up to temp on the road at Cruise speed. Water temp is 180 to 190. Oil press and water temp have not changed since before or after the noise started. I had the valve covers off When in Pa and everything looked good. Nothing looked out of place I checked the rocker studs and they were all tight. I didn't know this could be a roller cam so I didn't look at the lifters I am hoping to pull the covers off this weekend and check. As I said before it only makes noise above 2000rpm with a load on the engine. It ideals fine no miss no noise. Even if you rev it up a little bit it sounds like a normal engine. That's what is making this hard to pin down. Thanks for the input
 

Schurkey

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WHAT YEAR VEHICLE/ENGINE???
Still haven't answered this.

Flat-tappet cam, or roller cam?
'95-older = flat tappet unless it's been changed.
'96-newer = roller cam

Any chance what you're hearing is detonation, not valvetrain noise? Connect a scan tool, look for knock counts and/or a failed knock sensor.
Might not throw a "code". Still worth checking.

there is NO check engine light on and no codes.
I didn't ask about "codes". Connect a scan tool, look at the data stream; especially for knock sensor activity.

Also there is only One lifter-valve making noise.
How do you know?

it only makes noise above 2000rpm with a load on the engine.
The valvetrain shouldn't care whether there's a load on the engine. RPM might make a difference, though.

If this noise is load-sensitive, I bet it's isn't the cam/lifters. It might be a burnt valve.
 

Pinger

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The valvetrain shouldn't care whether there's a load on the engine. RPM might make a difference, though.
That it only happens under load is a big clue - to be deciphered.
For sure, it can't be valvetrain. Speed sensitive yes, load sensitive no.
 

Texvet

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Sorry that was a lame post
So the details are there is NO check engine light on and no codes. Also there is only One lifter-valve making noise. On the trip from Stl to Pit and back to Stl it used 1.5qt of oil. Oil pressure is 45 to 50 When up to temp on the road at Cruise speed. Water temp is 180 to 190. Oil press and water temp have not changed since before or after the noise started. I had the valve covers off When in Pa and everything looked good. Nothing looked out of place I checked the rocker studs and they were all tight. I didn't know this could be a roller cam so I didn't look at the lifters I am hoping to pull the covers off this weekend and check. As I said before it only makes noise above 2000rpm with a load on the engine. It ideals fine no miss no noise. Even if you rev it up a little bit it sounds like a normal engine. That's what is making this hard to pin down. Thanks for the input
Welcome to the site Kurt. This is a great place with tons of knowledge and helpful people. You got a little of what I call baptism by fire. These dudes will light you up if you don't feed them the pertinent info. LOL!
 

Kurt Wallis

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Still haven't answered this.


'95-older = flat tappet unless it's been changed.
'96-newer = roller cam


Might not throw a "code". Still worth checking.


I didn't ask about "codes". Connect a scan tool, look at the data stream; especially for knock sensor activity.


How do you know?


The valvetrain shouldn't care whether there's a load on the engine. RPM might make a difference, though.

If this noise is load-sensitive, I bet it's isn't the cam/lifters. It might be a burnt valve.
 

Schurkey

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Should be a roller cam, with a non-adjustable valvetrain. I'd expect hardened inserts for all the valve seats--intake and exhaust. Rotators under both the intake and the exhaust valve springs.

In short, the valvetrain should be very durable. Weird stuff happens; but at any rate a valvetrain noise shouldn't be dependent on engine load.

I'd do a cylinder leakdown test on each cylinder, to verify that the valves are sealing. Listen for escaping air at the tailpipe, (exhaust valve) and the throttle body (intake valve).
 
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